The present invention relates to lenticular lens sheets and, more particularly, to a lenticular lens sheet for a screen used in a rear projection television.
Since projection televisions are not so bright as CRT direct-viewing televisions, a screen as bright as possible has heretofore been demanded. Consequently, there has been a demand for a lenticular lens surface configuration exhibiting a high luminance and a large .alpha.H angle at which the gain is a half of the peak value in a gain chart (i.e. half-power angle)! such that the loss of incident light is minimized, and a large amount of light emanates in the forward direction. A configuration of a lenticular lens that meets such a demand is disclosed, for example, in Japanese Patent Application Post-Examination Publication No. 7-19029. In the prior art, both the entrance- and exit-side lens surfaces of a lenticular lens have an approximately elliptical sectional configuration, and a light-absorbing layer is formed on a light-blocking portion of the exit-side surface. Incident light is focused in the lenticular lens. The exit-side lens surface is formed in the vicinity of the focus point. In its light diffusion characteristic chart (gain chart), the lenticular lens has a bell-shaped characteristic curve that rises sharply near 45.degree..
On the other hand, there has recently been a demand for a lenticular lens configuration capable of providing uniform color and luminance over a wide angle range, in disregard of some loss of light, owing to the improvement in performance of projection tubes, etc. In particular, with the achievement of thin television sets, a screen having a larger convergence angle than the conventional ones and yet exhibiting excellent uniformity has been required. In the case of the above-described conventional lenticular lens configuration, the characteristic curves of R (red), G (green) and B (blue) in the gain chart rise rapidly near 45.degree. at respective points displaced relative to each other. Therefore, the luminance ratio of each color becomes large near 45.degree., causing the television screen to look undesirably colored as viewed from an oblique direction.